How much diesel does the daily test run of a generator burn in an Alwar oil mill, and can a battery charger save it?

The Bureau of Energy Efficiency (BEE) Alwar manual says some big mills start their generator for 5 to 10 minutes every day, burning about 200 litres a month idling against about 100 with healthy batteries. The 1,200 litres saved a year is rupees (Rs) 0.38 lakh and 3.2 tonnes of carbon dioxide (CO2).

What the manual found

• Some big mills run a diesel generator (DG) when grid power fails, and test it for 5 to 10 minutes every day. During idle running, fuel burns with no power out.
• Its figures: idle running about 200 litres a month. With the starting batteries kept healthy and charged by a battery charger, about 100 litres a month. A saving of 50% of the idle running.
• Cost to do it: nil, since the mill already has batteries. The manual also says to do the preventive checks and maintenance regularly so frequent trials can be cut.
• The manual still advises a 5 minute run once a week to preserve a standby engine.

The sums

• 100 litres a month x 12 = 1,200 litres a year, the figure printed. At the manual's Rs 32 a litre that is Rs 38,400, printed as Rs 0.384 lakh in its summary table.
• 1,200 litres is 100 litres a month for a year. The manual says only some big units have a DG, and the figure looks like one set, not a cluster of mills (our reading).

200 litres does not fit 5 to 10 minutes

Our arithmetic. 5 to 10 minutes a day for 30 days is 2.5 to 5 hours a month. 200 litres in 2.5 to 5 hours is 40 to 80 litres an hour. At about 3.3 kilowatt hours a litre, the figure on the live page about generator fuel use, that is the fuel for 130 to 260 kilowatts of output, far more than a set burns when idling. So the 200 litres probably includes more than the daily test, such as longer idling after cuts. Log your own.

What to log

1. Run log: date, start and stop times, minutes, and the reason (test, power cut, charging).
2. Litres filled: the diesel slips, with a tank reading at month end.
3. The DG energy meter's kWh, so test running shows as litres with no kWh.
4. Dates of battery checks and the battery charger.

The manual's litres, rupees and carbon dioxide

• Idle running: 200 litres a month x 12 = 2,400 litres. With healthy batteries: 100 x 12 = 1,200 litres
• Saving: 1,200 litres x Rs 32 = Rs 38,400
• CO2: 1,200 x 2.645 kg a litre = 3,174 kg, about 3.2 tonnes
• Implied burn: 200 litres / (2.5 to 5 hours) = 40 to 80 litres an hour

Litres, test minutes and the Rs 32 price are the manual's, at its date. 2.645 kg of CO2 a litre is the diesel factor Senseible uses: the Intergovernmental Panel on Climate Change 2006 net calorific value and emission factor, with the diesel density of 0.83 kg a litre from the Central Electricity Authority database.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the diesel bought for the set shows by month. It does not time test runs or measure what a set burns when idling.

• How many units a diesel generator should give per litre
• Diesel generator: Scope 1 or Scope 2
• Generator diesel and generator units: avoid double counting
• Alwar generator exhaust pipe wrap
• Carbon calculators

Sources: Bureau of Energy Efficiency and Confederation of Indian Industry, Manual on energy conservation measures in the Alwar oil mill cluster (SAMEEEKSHA), Intergovernmental Panel on Climate Change, 2006 Guidelines, Volume 2 Energy (fuel emission factors), Central Electricity Authority, CO2 Baseline Database for the Indian Power Sector (grid factor 0.675 kg CO2 per kWh, financial year 2025-26; diesel density 0.83 kg a litre, Appendix B)

Last reviewed 2026-11-06. Figures are the manual's, from the Bureau of Energy Efficiency Small and Medium Enterprises (SME) programme, at its diesel price of Rs 32 a litre. The manual's estimate is not a measurement; log your own test runs.